Anterior neural induction by nodes from rabbits and mice

The organizer of vertebrate embryos represents the major regulatory center for the formation of the embryonic axis during gastrulation. The early blas topore lip of amphibia and Hensen's node of the chick at the full-length pr imitive streak stage possess both a head- and a trunk-inducing potential. I n mice, a head-inducing activity was identified in the extraembryonic, ante rior visceral endoderm (AVE) by tissue ablation and genetic experiments. Ev idence for a similar activity in the AVE from the rabbit was obtained by tr ansplanting below the avian epiblast. However, it was still unclear whether the AVE is the exclusive origin of anterior neural induction or if this ac tivity is recapitulated by the node and/or its derivatives. We report here that nodes from both rabbit and mouse embryos can induce a complete neural axis including forebrain structures upon grafting to chick hosts. Thus, in rabbits and mice not only the AVE, but also the node, possesses a potential for the induction of anterior neural tissue. (C) 2000 Academic Press.